Polyphenols are a diverse group of naturally occurring compounds found in plants, including flavonoids, phenolic acids, and stilbenes. Their use to support the hepatic (liver) system is primarily justified by scientific research, although there is also a long tradition of using polyphenol-rich plants (such as green tea, turmeric, or milk thistle) in traditional medicine for liver health.

Scientific studies have shown that polyphenols possess antioxidant, anti-inflammatory, and hepatoprotective properties. Experimental research—mostly in vitro and in animal models—demonstrates that polyphenols can reduce oxidative stress and inflammation in liver tissue, protect hepatocytes from toxins, and modulate pathways involved in liver injury (e.g., NF-κB, Nrf2). For example, silymarin (a mixture of flavonolignans from milk thistle) and resveratrol (a stilbene from grapes) have been extensively studied for their ability to attenuate liver damage induced by toxins, alcohol, or metabolic disorders.

Human studies are less abundant and often limited by small sample sizes or lack of standardization across polyphenol types and doses. Nonetheless, some clinical trials report beneficial effects of polyphenol-rich extracts or diets in markers of liver function, particularly in non-alcoholic fatty liver disease (NAFLD) and liver enzyme profiles. Overall, while preclinical evidence is strong, human evidence is moderate and more high-quality trials are needed.